1. Field of the Invention
This invention relates to a scroll type pump to be utilized for, for example, compressors for freezing or air conditioning, pumps or blowers for industry, or the like.
2. Description of the Prior Art
FIG. 5 is a cross sectional view showing a conventional co-rotational scroll type pump disclosed in, for example Japanese Published Unexamined Patent Application (JP-A) No. 191685/87 (Tokkai-sho 62-191685). FIG. 6(a)-FIG. 6(d) are sectional views showing the operation of the principal part of the compressor.
In FIG. 5, reference numeral 1 denotes a driving scroll member composed of a disc 1a provided with a fluid compressing wall 1b formed in a spiral shape as shown in FIG. 6(a)-FIG. 6(d) on the one side surface 2aa of the disc la. Reference numeral 2 denotes a follower scroll member composed of a disc 2a provided with a fluid compressing wall 2b formed in a spiral shape as shown in FIG. 6(a)-FIG. 6(d) on the one side surface 2aa of the disc 2a for being driven to rotate by the driving scroll member 1. Reference numeral 2c denotes the center of gravity of the follower scroll member 2.
Reference numeral 3 denotes a fluid compressing chamber shaped generally to a crescent with the fluid compressing walls 1b and 2b as shown in FIG. 6(a)-FIG. 6(d). Reference numeral 4 denotes a driving shaft as a rotation axis of the driving scroll member 1. Reference numeral 5 denotes a follower shaft as a rotation axis of the follower scroll member 2, in which follower shaft 5 a discharging passage 5a for discharging the fluid in the fluid compressing chamber 3 is formed to perforate the follower shaft 5. The distance L between the shaft center O.sub.1 of the driving scroll member 1 and the shaft center O.sub.2 of the follower scroll member 2 is set to L=P/2-t, where reference letter P denotes the pitches of the fluid compressing walls 1b and 2b of the scroll members 1 and 2, and reference letter t denotes the thicknesses of the fluid compressing walls 1b and 2b. Reference numeral 6 denotes a housing for accommodating the whole apparatus. Reference numeral 7 denotes a thrust bearing for supporting the other surface 1ab side of the disc 1a. Reference numeral 8 denotes a lower bearing supporter fixed to the housing 6 for supporting the thrust bearing 7 and provided with bearings 9a and 9b supporting the driving shaft 4. Reference numeral 10 denotes a thrust bearing for supporting the other surface 2ab side of the disc 2a. Reference numeral 11 denotes an upper bearing supporter for supporting the thrust bearing 10.
The upper bearing supporter 11 is provided with a bearing 12 and a bearing 13 for supporting the follower shaft 5 at two points on the surface 2ab side of the disc 2a. Reference numeral 14 denotes a supporter fixed to the housing 6 for supporting the upper bearing supporter 11 with a bolt 15.
Reference numeral 16 denotes an electric motor which is a driving source of the disc 1a, and which is composed of a stator coil 17, a stator core 18 mounting the stator coil 17 and a rotor 19 fixed to the driving shaft 4, and further which is held by an electric motor holding part 20.
Reference numeral 21 denotes an oil reservoir provided at the top portion of the upper shaft supporter 11. Reference numeral 22 denotes an end plate attached to the top portion of the oil reservoir 21 with the bolt 23. Reference numeral 24 denotes a rotating mechanical seal attached to the shaft end of the follower shaft 5. Reference numeral 25 denotes a fixed mechanical seal attached to the end plate 22 and touching the mechanical seal 24 for preventing the leakage of compressed fluid. Reference numerals 26a-26e denote a sealing member for preventing the leakage of compressed fluid, which sealing member 26a-26e is inlaid into a slot (not shown) for sealing formed at the top of the fluid compressing wall 1b. Reference numerals 27a-27e denote a sealing member for preventing the leakage of compressed fluid, which sealing member 27a-27e is set in a slot (not shown) for sealing formed at the top of the fluid compressing wall 2b.
Reference numeral 28 denotes an oil pump to be driven by the driving shaft 4. Reference numeral 29 denotes an oil filler pipe for feeding lubricating oil from the oil pump 28 into the oil reservoir 21. Reference numeral 30 denotes an introducing passage attached to the housing 6 for introducing fluid into the fluid compressing chamber 3 from the outside. Reference numeral 31 denotes lubricating oil accumulated in the bottom of the housing 6.
Next, the principle of the operation of the conventional pump will be described.
When the electric motor 16 is rotated, the driving scroll member 1 is rotated around the shaft center O.sub.1. Since the shaft center O.sub.1 of the driving scroll member 1 is parted from the center O.sub.2 of the follower scroll member 2 by the distance L, as shown in FIG. 6(a), sealing portions S.sub.1 -S.sub.6 in a radial direction of the fluid compressing walls 1b and 2b are formed in a state of a straight line in the tangential direction on involute basic circle (not shown).
As shown in FIG. 6(b), the external periphery side of the fluid compressing wall 2b touches the internal periphery side of the fluid compressing wall 1b at sealing portions A.sub.1 -A.sub.3 on the left side of the shaft center O.sub.2. Since the internal periphery side of the fluid compressing wall 1b moves so as to decrease its diameter when it is seen from the shaft center O.sub.1 owing to the sealing portion A.sub.1 -A.sub.3, the internal periphery side inevitably touches the external periphery side of the fluid compressing wall 2b to drive the follower scroll member 2 to rotate.
In a state that the driving scroll member 1 and the follower scroll member 2 are performing the compressing movement together. Since the driving scroll member 1 is rotated by the electric motor 16 and the follower scroll member 2 receives only the compressing torque, the follower scroll member 2 tends to rotate around the shaft center O.sub.2 in a direction contrary to the driving scroll member 1. In this case, the follower scroll member 2 touches the driving scroll member 1 at the sealing portions B.sub.1 -B.sub.3 shown in FIG. 6(b), and the contrary rotation of the follower scroll member 3 is prevented by the sealing portions B.sub.1 -B.sub.3 to continue the compressing movement.
Besides, when the driving scroll member 1 begins to decreasing its speed for stopping or the like, the follower scroll member 2 tends to rotate fast owing to the inertia of the movement thereof, but as shown in FIG. 6(b), since the scroll members 1 and 2 touches each other at the sealing portions B.sub.1 -B.sub.3 on the right side of the shaft center O.sub.1, they rotate synchronously. This rotation is performed in the order of: FIG. 6(a).fwdarw.FIG. 6(b).fwdarw.Fig. 6(c).fwdarw.FIG. 6(d).fwdarw.FIG. 6(a).
On the other hand, by the rotation of the driving shaft 4, the oil pump 28 is actuated to send the lubricating oil 31 to the oil reservoir 21 through the oil filler pipe 29 for lubricating the rotating mechanical seal 24 and the fixed mechanical seal 25. After the lubricating oil 31 lubricated the thrust bearing 7, the bearings 9a, 9b, the thrust bearing 10, the bearing 12 and the bearing 13, the lubricating oil 31 is returned to the inside bottom of the housing 6.
By taking the construction as described above, each of the driving shaft 4 and the follower shaft 5 is prevented from being seized by the rocking of both the scroll members 1 and 2.
Since the relative motion of the driving scroll member 1 and the follower scroll member 2 as shown in FIG. 6(a)-FIG. 6(d) can be fluently operated by providing the oil reservoir 21, the fluid compressing chamber 3 gradually moves from the external periphery side to the center side, and the volume of the chamber 3 gradually decreases. Consequently, the pressure for compressing the fluid introduced from the introducing passage 30 can gradually be increased, thereby the fluid can be pressed to be discharged from the discharging passage 5a as a high pressure gas.
The conventional scroll type pump as described above is constructed so that the bearings 12 and 13 for supporting the follower scroll member 2 are disposed only on the one side of the center of gravity 2c of the follower scroll member 2, it is difficult to support the follower scroll member 2 in a balanced state, and consequently rocking of the follower scroll member 2 is generated.
Moreover, since a force is generated on the thrust bearings 7 and 10 as a reaction force to the compressing force of the fluid, an over load is imposed on the sealing portions S.sub.1 -S.sub.6 of the driving scroll member 1 and the follower scroll member 2.
Accordingly, for preventing the abrasion of the sealing portions S.sub.1 -S.sub.6 of the driving scroll member 1 and the follower scroll member 2 where the over load is imposed, the lubricating oil 31 lubricating the bearings 12 and 13 is indispensable. If the conventional pump is used in an oil-free state not using the lubricating oil, the abrasion becomes remarkable, and consequently, there are problems that the early abrasion of the scroll members 1 and 2 and noises are generated, and that there is a case that the scroll members 1 and 2 are seized to be locked in the worst case.